Arctic LTER Database

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The re-use of scientific data has the potential to greatly increase communication, collaboration and synthesis within and among disciplines, and thus is fostered, supported and encouraged. Permission to use this dataset is granted to the Data User free of charge subject to the following terms:

1) Acceptable use. Use of the dataset will be restricted to academic, research, educational, government, recreational, or other not-for-profit professional purposes. The Data User is permitted to produce and distribute derived works from this dataset provided that they are released under the same license terms as those accompanying this Data Set. Any other uses for the Data Set or its derived products will require explicit permission from the dataset owner.
2 ) Redistribution. The data are provided for use by the Data User. The metadata and this license must accompany all copies made and be available to all users of this Data Set. The Data User will not redistribute the original Data Set beyond this collaboration sphere.
3 ) Citation. It is considered a matter of professional ethics to acknowledge the work of other scientists. Thus, the Data User will properly cite the Data Set in any publications or in the metadata of any derived data products that were produced using the Data Set. Citation should take the following general form: Creator, Year of Data Publication, Title of Dataset, Publisher, Dataset identifier. For example:

4 ) Acknowledgement. The Data User should acknowledge any institutional support or specific funding awards referenced in the metadata accompanying this dataset in any publications where the Data Set contributed significantly to its content. Acknowledgements should identify the supporting party, the party that received the support, and any identifying information such as grant numbers. For example:

Data sets were provided by the Arctic LTER. This material is based upon work supported by the National Science Foundation under Grants #DEB-981022, 9211775, 8702328; #OPP-9911278, 9911681, 9732281, 9615411, 9615563, 9615942, 9615949, 9400722, 9415411, 9318529; #BSR 9019055, 8806635, 8507493.

5 ) Notification. The Data User will notify the Data Set Contact when any derivative work or publication based on or derived from the Data Set is distributed. The Data User will provide the data contact with two reprints of any publications resulting from use of the Data Set and will provide copies, or on-line access to, any derived digital products. Notification will include an explanation of how the Data Set was used to produce the derived work.
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While substantial efforts are made to ensure the accuracy of data and documentation contained in this Data Set, complete accuracy of data and metadata cannot be guaranteed. All data and metadata are made available "as is". The Data User holds all parties involved in the production or distribution of the Data Set harmless for damages resulting from its use or interpretation.

This file contains PAR , relative humidity, and temperature data logged every five minutes from within, below, and above Betula nana and Salix pulchra shrub canopies at two locations near Toolik Lake, Alaska during the summer of 2012. The location of the PAR sensor and dataloggers were co-located with the LTER shrub plots (block 1 and 2), also used for the chamber flux and point frame measurements taken this same year. There were two logging sites (block 1 and 2), each of which had five PAR sensors, two for each shrub canopy and one above, as well as three sensors to log relative humidity and temperature. Additional data about the daily instrument output from these sites can be found in the file "ShrubCanopy_DailyLogger".

For questions about the Metadata and data contact the Investigators. For information about this web site contact:

This was a season-long project, though it followed similar methods to ITEX projects performed starting in 2003 that are likely to be replicated in the future for reasearch at the Toolik Field Station, AK.

Log of Changes:

Version 2: Missing values changed to #N/A. CH 28Jan2013

Version 3: Metadata updated to newer form (with sites sheet). CH April 2013.

Version 4: corrected eml for .xlsx JimL

Version 5: Removed thousand separator in number. JimL 17May13

Version 6: Corrected Distrubution URL. It had xlsfiles in the path. Jim L 19Jun14

RESEARCH LOCATION:

Location Name

LTER Shrub Block 1

LTER Shrub Block 2

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Geographic Description

Upland site; co-located in Block 1 of the Shrub LTER sites; IVO 68° 38'18.8" N, 149° 34' 07.2" W +/- 50m. Plots are outside of the designated LTER treatments, though are exposed to the same environmental conditions. All plots were chosen by the dominant shrub canopy (either Salix pulchraor Betula nana) and preferentially selected to be 90cm+ in height.

Outlet site; co-located in Block 2 of the Shrub LTER sites; IVO 68° 38'008.1" N, 149° 35' 017.1" W +/- 50m. Plots are outside of the designated LTER treatments, though are exposed to the same environmental conditions. All plots were chosen by the dominant shrub canopy (either Salix pulchraor Betula nana) and preferentially selected to be 90cm+ in height.

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Location Bounding Box

West Bounding Coordinate

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Latitude

68.6385555555555

68.6355833333333

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Longitude

-149.568666666666

-149.588083333333

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Elevation

747 m

730 m

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Link to Google Map

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TAXONOMIC COVERAGE:

Organisms studied

Betula nana; Salix pulchra

Methods:

Automated Data LoggingIn order to monitor canopy conditions of the shrub species of interest--Betula nana and Salix pulchra--two CR1000 dataloggers (Campbell Scientific, 815 W. 1800, North Logan, UT, USA) were installed at the sites used for the ITEX shrub canopy studies at Toolik Field Station in Alaska the summer of 2012. The sites (see "Group" category) are labeled as "Upland" and "Outlet"--descriptions of the sample site in relation to Toolik Lake. The Upland site is colocated with Block 1 of the LTER shrub vegetation plots; the Outlet site is colocated with Block 2. The dataloggers were adjacent to, rather than within, LTER plots.

Both the Upland and Outlet datalogger had the following sensors which logged every five minutes:(5) Photosynthetically active radiation (PAR) sensors: LI-190SB Quantum Sensor (Li-Cor Biosciences, 4647 Superior St, Lincoln, NE, USA) * Sensors were placed as follows: (1) Above all vegetation at a height of 2.2 meters

Additionally, the maximum and minimum recorded values as well as the total daily photon flux were recorded each day. These data are available in the file "ShrubCanopy_DailyLogger".

SunScan LAI and PAR Measurements: As with other measurments collected the summer 2012 for the ITEX project at Toolik Field Station, a Delta-T SunScan wand (Delta-T Devices Ltd, Burwell Cambridge, UK) was use to characterize the shrub canopies with the dataloggers. These data are included in the datasets: "SunScan_LAI" and "SunScan_PAR". The methods used for each are described below.

The methods used to collect PAR at many heights within each canopy were the same used to collect LAI, with the difference being the setting on the SunScan wand. The measurements were taken near the end of the growing season when leaves were already beginning to senesce. Additionally, while these measurements are traditionally made in conjunction with a Beam Fraction sensor (BF3), this sensor was malfunctioning when the datalogger sites were sampled , and thus it was not used. Instead of the BF3 sensor, wand measurements above the canopy were made immediately prior to each data measurement to record the ambiant total irradiance levels.

Readings were taken by inserting the SunScan wand near to the ground as possible--typically starting at 5 centimeters from the ground (the wand rested atop the moss layer)--and then repeated every 15 cm with the last measurement being above the canopy. Measurements were taken with the field technician opposite the direction of the sun at five locations within the canopy at each height. Five replicates were taken at each height in the canopy immediately surrounding the datalogger sensors; this differs from the ITEX samples which had three replicate scans at each height.

The weather conditions during these measurements were almost uniform cloud cover; thus nearly all of the measurements were taken under "diffuse" light conditions (diffuse light fraction greater than 0.7). The measurements taken with "direct" light conditions were taken on partly cloudy days.

The SunScan wand measures PAR along 64 points along a 1-m horizontal profile. When sampling PAR within the shrub canopy, the data are from the raw output from each PAR sensor. When sampling LAI, there is an internal calculation performed though the Delta-T software that compares the reading above the canopy to the reading within the canopy, and takes into account the percent of absorbed PAR (assumed to be 0.85), and the ellipsoidal leaf angle distribution parameter (ELADP*) (assumed to be 1.0).

In addition to the LAI values, the Delta-T SunScan instrument gives an output of other variables including: transmitted light, spread among sensors, beam fraction, and zenith angle. These values are further described here:

Transmitted Light: the fraction of incident light that passes through a given canopy. It can refer to Direct, Diffuse, or Total incident light.

Spread: the standard deviation of the 64-PAR sensors on the SunScan wand.

Beam Fraction: the fraction of the Total incident PAR in the Direct beam.

Zenith Angle: the angle between the centre of the sun and the point directly overhead. Zenith angles are calculated from latitude, longitude, and local time using standard astronomical equations as given in Practical Astronomy. The location used to determine the local zenith angle was: 68° 37' 39" N, Longitude 149° 35' 51" W.

*"ELADP is a way of characterizing the horizontal or vertical tendency of leaves in a canopy." p 37 of SS1 User Manual v2.0 (SunScan Canopy Analysis System, type SS1. Delta-T Devices Ltd. May 19, 2008)